Pump impeller construction

ABSTRACT

Gear pump impellers formed of Teflon because of the softness and slipperiness of the material are difficult to connect to a metallic shaft. Yet Teflon is a very good material for gear pump impellers because of its low co-efficient of friction, chemical inertness and ability to withstand high temperatures and extreme temperature variations. In this invention a portion of the plastic is confined between a rigid central shaft spline and a cup rotatable with the shaft so that the plastic cannot flow without two-dimensional or three-dimensional distortion or tearing, both of which are resisted by the plastic.

United States Patent 11 1 Martin et al. I

[ PUMP IMPELLER CONSTRUCTION [75] Inventors: Thomas B. Martin, Danville;

Ferdinandus A. Pieters, Concord,

both of Calif.

[73] Assignee: Micropump Corporation, Concord,

Calif.

[22] Filed: Feb. 8, 1973 211 App]. No.: 330,759

[521 u.s. C1 418/152, 29/156.8 R, 29/4321,

29/445 511 im. Cl B23p 9/00, FOlc 21/00, F040 15/00 58 Field of Search 418/l52156,

[56] References Cited UNITED STATES PATENTS 1,400,032 12/1921 Dickey 416/241 A 2,172,977 9/1939 Kimball 2,663,263 12/1953 Mayus et al. 418/154 Apr. 2, 1974 2,712,792 7/1955 Snyder 418/154 2,948,227 8/1960 Neely 418/155 2,966,860 1/1961 Maynard 418/152 Primary Examiner-Carlton R. Croyle Assistant Examiner.1ohn .l. Vrablik Attorney, Agent, or FirmJulian Caplan [57] ABSTRACT Gear pump impellers formed of Teflon because of the softness and slipperiness of the material are difficult to connect to a metallic shaft. Yet Teflon is a very good material for gear pump impellersbecause of its low co-efficient of friction, chemical inertness and ability to withstand high temperatures and extreme temperature variations. In this invention a portion of the plastic is confined between a rigid central shaft spline and a cup rotatable with the shaft so that the plastic cannot flow without two-dimensional or threedimensional distortion or tearing, both of which are resisted by the plastic.

8 Claims, 4 Drawing Figures PUMP IM'PELLER CONSTRUCTION This invention relates to a new and improved pump impeller construction and has particular application when the impeller is formed of Teflon.

The principal object of the present invention is to make possible the use of Teflon in pump impellers despite the fact that such materials tend to stretch and take a set due to cold flow characteristics. Prior impellers of this type have failed because, with the passage of time, the fit between the plastic material and the shaft of the impeller loosens and tends to deform with further passage of time until failure occurs. These faiures are largely eliminated with the use of the present invention.

Accordingly, it is a principal purpose of the present invention to confine the Teflon between the shaft and a rigid cup secured to the shaft so that the Teflon captured between the shaft and the cup cannot move without causing atwo-dimensional or three-dimensional distortion of the confined material or without tearing the material loose. Since Teflon resists such distortion and tearing, a secure bond between the shaft and the impeller is obtained.

Another feature of the invention is the fact that means is provided to secure the impeller to the shaft within the root diameter of the gear. Accordingly, no enlargement of the impeller gear is required for the purpose of making a mechanical connection of the gear to the shaft.

Other advantages of the use of Teflon are obtained by practice of the present invention. Among these advantages are the fact that the material has a low coefficient of friction, is chemically inert and has the ability to withstand not only high temperatures but extreme temperature variation.

Other objects of the present invention will become apparent upon reading the following specification and referring to the accompanying drawings in which similar characters of reference represent corresponding parts in each of the several views.

In the drawings:

FIG. 1 is an exploded perspective view of -a gear blank, shaft and cups in accordance with the present invention.

FIG. 2 is an enlarged vertical sectional view through the assembled gear blank and shaft.

FIG. 3 is an end elevational view of a pump in which gears of the present invention are installed on their shafts, partially broken away to reveal internal construction.

FIG. 4 is a sectional view taken substantially along the line 4-4 of FIG. 3.

Shaft 11 of the present invention is preferably formed of a metal such as steel and has a hexagonal spline 12 formed integral therewith and circular cross-sectional ends 13. The object of the present invention is to assemble such a shaft 11 on a gear blank 16 of Teflon to achieve the purposes heretofore described. Preliminary to assembly, gear blank 16 is formed with a hexagonal bore 17 shaped to receive spline 12 with a press fit. Further, on either end of the blank 16 (which preferably is externally cylindrical) depressions 18 are formed.

Fitting over either end 13 of shaft 11 is a cup 21 having an annular end 22 with a central hole dimensioned to fit over end 13 with a press fit and a cylindrical flange 23 dimensioned to fit inside the depression 18 with a press fit. The edges of flange 23 are formed with serrations 24. In assembly of the parts, spline 12 is forced into bore 17. Cups 21 are forced inwardly from each end so that the cups are secured to ends 13 and the serrations 24 dig into the blank 16 and form a groove 26 in the blank. Thus, the end 22 fits tightly on the end 13 of shaft 11 and similarly, the flange 23 fits tightly into the groove 26 and the serrations 24 prevent rotation. An important feature of the invention is the fact that there is an annylar portion 27 of material con-' fined etween the spline l2 and the cup flange 23. Such portion cannot drift without causing two or three dimensional distortion of the material or without tearing loose from the main body of the blank 16, functions which do' not ordinarily occur in Teflon construction.

After the blank 16 has been secured to the shaft 11 as shown in FIG. 2, teeth 29 are cut in the blank 16 in accordance with well known gear cutting principles. The blank 16 is distorted by forcing the cups 21 into it. Therefore it is desirable to perform further processing such as turning to proper outside diameter and cutting the teeth 29 after the blank 16, cups 21 and shaft 11 are assembled.

FIG. 3 and 4 show a typical installation for a pair of gears fabricated in accordance with the present invention. It will be understood that the structure of FIGS. 3 and 4 is merely illustrative of one environment using the invention and that the invention may be adapted 'to other environments. In the pump construction shown in FIGS. 3 and 4, a casing 31 has pump inlet and outlet 32 and 33 on opposite sides with pump chamber 34 between the two.

Gears 39 are mounted in chamber 34. One form of mounting provides integral bushings 36 for ends 13. One gear-39 (the upper gear in FIG. 4) is a drive gear and its shaft end extends through a journal 37 and is connected to a prime mover such as a motor (not shown). To provide against wear and reduce leakage, plates 38 may be installed within chamber 34 to either side of the gears 39.'Plates 38 overcome any tendency of cups 21 to be displaced or to damage housing 31. The structure has the advantages hereinbefore mentioned.

What is claimed is:

l. A pump impeller comprising a rigid shaft having a non-circular portion, a blank of Teflon having a central bore shaped to fit over said non-circular portion with a tight fit, and at least one cup of rigid material having an annular end formed with anaperture to fit on the end of said shaft near said non-circular portion with a tight fit and having an intumed cylindrical flange having an inside diameter greater than said non-circular portion and an outside diameter substantially less than that of said blank, said flange forced into said blank from one end thereof, a portion of said blank being confined between said non-circular portion and said flange.

2. An impeller according to claim 1 in which the edge of said cup is formed with serrations digging into said blank.

3. An impeller according to claim 1 in which said I non-circular portion is hexagonal in cross-section and said flange is annular in cross-section.

4. An impeller according to claim 1 in which there is a cup on each end of said blank.

5. An impeller according to claim 1 in which said blank is formed with gear teeth on its periphery.

6. A method of fabricating a gear blank and shaft combination comprising providing a shaft having a non-circular cross-section portion and round crosssection ends at either side of said non-circular portion, forcing an aperture blank of Teflon onto said noncircular portion, forcing over either of said ends a cup having an annular disk and inturned flanges so that said flanges are embedded in grooves formed in said blank of largerdiameter than the size of said non-circular portion and some of the material of said blank is confined between said non-circular portion and said been embedded in said blank. 

1. A pump impeller comprising a rigid shaft having a noncircular portion, a blank of Teflon having a central bore shaped to fit over said non-circular portion with a tight fit, and at least one cup of rigid material having an annular end formed with an aperture to fit on the end of said shaft near said noncircular portion with a tight fit and having an inturned cylindrical flange having an inside diameter greater than said non-circular portion and an outside diameter substantially less than that of said blank, said flange forced into said blank from one end thereof, a portion of said blank being confined between said non-circular portion and said flange.
 2. An impeller according to claim 1 in which the edge of said cup is formed with serrations digging into said blank.
 3. An impeller according to claim 1 in which said non-circular portion is hexagonal in cross-section and said flange is annular in cross-section.
 4. An impeller according to claim 1 in which there is a cup on each end of said blank.
 5. An impeller according to claim 1 in which said blank is formed with gear teeth on its periphery.
 6. A method of fabricating a gear blank and shaft combination comprising proviDing a shaft having a non-circular cross-section portion and round cross-section ends at either side of said non-circular portion, forcing an aperture blank of Teflon onto said non-circular portion, forcing over either of said ends a cup having an annular disk and inturned flanges so that said flanges are embedded in grooves formed in said blank of larger diameter than the size of said non-circular portion and some of the material of said blank is confined between said non-circular portion and said flanges and so that said cups rotate with said shaft.
 7. A method according to claim 6 which further comprises forming a depression in each end of said blank preliminary to forcing said blank on said shaft, each said depression being slightly smaller than the outside of the flange of said cup and of lesser depth than the length of said flange.
 8. A method according to claim 6 which further comprises machining said blank to true outside diameter and cutting gear teeth in the blank after said cup has been embedded in said blank. 